1. Field of the Invention
This invention relates to a process of making an urethane group-containing polyisocyanurate foam from a polyisocyanate and a polyhydroxy compound wherein the polyhydroxy compound is an acid, neutral, or basic salt, or a mixture thereof of naphthenic acid and a hydroxyl group-containing amine selected from the group consisting of a secondary amine, a tertiary amine and a mixture thereof; or a mixture of the aforementioned salts and conventional polyols.
2. Description of the Prior Art
The manufacture of semi-rigid and rigid polyurethane foams from polyols, particularly polyfunctional polyether polyols, organic polyisocyanates, catalysts, blowing agents and auxiliaries and additives is described in detail in the appropriate literature (Plastics Handbook, Vol. VII, "Polyurethanes" by R. Vieweg and A. Hoechtlen, Carl Hanser Publishers, Munich, 1966).
Swiss Pat. No. 343,635 relates to the use of salts of secondary or tertiary amines which may contain hydroxyl groups in bonded form and monocarboxylic acid, polycarboxylic acids, sulfonic acids, or acid sulfuric ester as initiators for the manufacture of polyurethane foam in quantities of 1 weight percent to 10 weight percent relative to the polyhydroxy compound. When hydroxyl group-containing salts are used, the hydroxyl groups are masked prior to the urethane reaction by addition or condensation reaction.
Fatty acids, fatty acid esters, fatty acid amides or salts of fatty acids may also be used for making of polyurethane foam. German Patent Application No. 1,173,643 relates to the manufacture of flexible foams with the hand desired for textile processing and a velvet-like surface structure from toluene diisocyanate, a special polyester polyol, and a particular blowing agent mixture in the presence of 1 weight percent to 10 weight percent, relative to the polyester polyol, of tall oil. British Pat. No. 882,949 relates to making foams from natural water-containing salts of hydroxy fatty acids such as hydroxy stearic acid, resinoleic acid, and castor oils, and secondary and tertiary amines. British Pat. No. 1,248,919 relates to making foams from amides of fatty acids having 8 to 24 carbon atoms and dialkanol amines which also may contain salts of dialkanol amines and fatty acids as well as fatty acid esters. The salts themselves form extremely brittle foams which frequently collapsed. U.S. Pat. No. 3,178,300 relates to producing polyurethane foams with a skeletal structure of cell webs instead of cell walls from polyisocyanates and castor oil in the presence of monoalcohols having 1 carbon atom to 18 carbon atoms or of monocarboxylic acids having 2 carbon atoms to 18 carbon atoms.
A drawback of the above mentioned foams, particularly those based on tall oils, is that they usually have a very unpleasant odor. Furthermore, polyurethane foams containing high amounts of natural materials have somewhat less favorable compression strength characteristics than products containing synthetic polyols only.
The area of application of such foams is limited by their burning characteristics in relation to classification of construction materials. This drawback may be eliminated by adding fire protection agents in larger quantities. These include antimony oxide, chlorinated compounds such as the Diels-Alder adduct of hexahalogencyclopentadiene and maleic anhydride or of halogenated phosphorus compounds such as tris(2-chloroethyl)phosphate, tris(dichloropropyl)phosphate, or tris(2,3-dibromopropyl)phosphate.
However, the problem is only partially solved by these measures because the achieved flame resistance results in a considerable reduction of other physical properties such as compression strength and dimensional stability under influence of heat. Furthermore, this measure is expensive.
The manufacture of urethane group-containing polyisocyanurate foams is not new either.
Such polymer foams have a comparatively high dimensional stability under influence of heat and improved flame resistance. However, polyisocyanate foams are very brittle. The brittleness can be reduced by increasing the polyol content. A drawback of this, however, is that the flame-inhibiting properties are reduced thereby.